Imaging performance of a PET/SPECT dual modality animal system

SPECT imaging capability was developed on a LabPET animal scanner to provide an integrated PET/SPECT bimodality imaging environment, supporting a broader range of imaging applications with an expanded library of radiopharmaceuticals. The SPECT imaging mode was enabled by 1) mechanically integrating collimator assemblies in the PET detector ring, and 2) properly tuning the detectors to acquire singles events in the 120-160 keV range. Two interchangeable collimators were designed for performing different imaging applications: a multiple pinhole collimator for its high resolution suitable for mouse imaging, and a slit-slat collimator for its large FOV adequate for rat imaging. To mitigate the non-uniform detector crystal layout in both the azimuthal and axial directions, a helical scan scheme, which combines collimator rotational movement and subject linear motion, was used for more uniformly sampled volume imaging. Unique calibration techniques taking advantage of the PET imaging capability were developed for determining the geometrical parameters of collimators. We report on the design parameters and initial performance assessment of this cost-effective SPECT imaging solution. Phantom and animal images demonstrating the relevance of the system for various imaging tasks in preclinical research are presented.